During the coming project period, we plan to develop methods for selectively isolating B cells bearing receptors having the cross-reactive idiotype present in the anti-p-azophenylarsonate (anti-Ar) antibodies of all A/J mice. The basic technique will utilize polystyrene tubes coated with antiidiotypic antibody to adsorb the cells; elution will be carried out with hapten. Breeding studies of A/J mice will be continued in an effort to produce lines synthesizing anti-Ar antibodies with a high or low content of the cross-reactive idiotype. We will continue our investigations of methods for enhancing the immunogenicity of BALB/c myeloma proteins in BALB/c mice; various chemical modifications of the proteins will be employed. The purpose is to facilitate studies of the mechanism of rejection of myeloma tumors by mice producing antiidiotypic antibodies to the myeloma protein formed by the tumor. The roles of humoral and cell-mediated immunity in the rejection phenomenon will be assessed. We will continue to study, in the secondary response, the production of anti-Ar antibodies in vitro. The role of factors such as antiidiotypic antibodies and suppressor T cells will be assessed in these in vitro investigations. BIBLIOGRAPHIC REFERENCES: A. Tung and A. Nisonoff, "Isolation from Individual A/J Mice of Anti-P-Azophenylarsonate Antibodies Bearing a Corss-Reactive Idiotype." J. Exper. Med. 141, 112 (1975). J. D. Capra, A. S. Tung and A. Nisonoff, "Structural Studies on Induced Antibodies with Defined Idiotypic Specificities. I. The Heavy Chains of Anti-p-Azophenylarsonate Antibodies from A/J Mice Bearing a Cross-Reactive Idiotype." J. Immunol., 114, 1548 (1975).